C.V.
Since he's already very pragmatic and rule-oriented, you teach him "The Friend Rules."
These lessons occur over time, of course.
There are LOTS of great books out there for this purpose, which talk about what facial expressions and body language means, and how he should react to those. For instance, if someone is crying and has a sad face (downturned mouth, quivering lips/chin, sad eyes), they are sad. It's a Friend Rule to soften your voice, sit next to them, and ask "are you okay? Is there anything I can do to help you feel better?" Or just listen if they need to talk without interrupting.
There are Friend Rules for every situation....working with your HFA child is simply about expanding their mental library of resources so they know how to "read" others and what to do.